INSECT ENEMIES AND THEIR CONTROL 



113 



chemical reaction of the sulphuric acid and water and it 

 is important for the liquid to cool considerably before the 

 cyanide is added in order to prevent too rapid generation 

 of the gas. 



Some growers drop the cyanide into jars without the 

 use of paper bags or packages. It is much safer, how- 

 ever, to use paper containers, for these will resist the 

 action of the acid for a few seconds and make it a safer 

 operation for the fumigator. The proper amounts of 

 cyanide may be weighed on suitable scales or it may be 

 more convenient to have them prepared in proper 

 amounts by the druggist. 



When everything is in readiness, all doors are closed 

 and locked except the ones through which the operator is 

 to pass. If there are several rows of crocks there must 

 be a man for each row. The 

 packages are carried in a basket 

 or a convenient receptacle, and 

 the operator usually starts at the 

 end of the house farthest from 

 the packing or service rooms. He 

 passes rapidly from vessel to ves- 

 sel, carefully placing a packet in 

 each crock so as to avoid splash- 

 ing the contents or breathing the 

 gas that might escape before he 

 proceeds to the next crock. After 

 the last crock is passed, he leaves 

 the house and locks the door 

 which has been left open for his 

 exit. The house should be care- 

 fully guarded for a few hours. 

 There is absolutely no danger in 

 this operation if proper care is ex- 



Fig. 35. Female nematode 

 (Heterodera radicicola) mag- 

 nified 85 diameters: a, 

 mouth; b, spherical sucking 

 bulb; c, ovaries as seen 

 through the body wall; d, 



' s generally not difficult to 



P, ... isolate them in water by 



Some growers prefer tO raise breaking open the galls con- 



the ventilation in two or three 



them ' (After N ' A ' 



